Impulse recording optical system



A; MAURER, JR xurunsn xmconnme omen. mm

Original Filed Aug. 2, 1940 3 Sheets-Sheet 1 FIG. I

lea

, uvmvroxf JOHN A. MAUREEN/R- "M/W AGENT 3 Sheets$heat 2 FIG. 6

' FIGQ Fia'm [I ia J. A. MAURER, JR

IIPULSE RECORDING OPTICAL SYSTEI oz iginal Filed Aug. 2, 1940 FIG. 7

but

INVENTOR JOHN =4. MAURER,JR A GENT FIG. l5

J. ATMAURER; JR IMPULSE RECORDING OP TICAL SYSTEM Aug. 26,1947.

Original Fneqm 2, 1940- :5 shets-sneat's he l6 FIG. 14

INVENTOR JOHN A. MA URER JR.-

BY AGENT l atented Aug. 26, 1947 tion of New York 7: a

I John A. Mau'rer, in; New 'York N. Y.,

J. A. Maui-er, Inc., Ne

ork, Ne Y, a camera;

, Original 'a' pplic'a tlon" has 2', i940, Serial 1%; I 349,515.17 Divided'and this application Dccemv her 4, 1944; SerialNo. 566,459

This invention relates to optical systems for the photograp ic recording of electricaljimpulses "on a, moving film such as are used in sound r cor ing, picture transmission, and the like, and this application is a division oi-my application Serial No. 349,515, filed August 2, 1940,?Whlh is also assignedtoJ.A.Maurer,'Inc,

More particularly, the invention relates to op-v ticalsystems of the class referred to above where-- in asmall mirror vibrated byan oscillograph' galvanometer, or asimilar .device for translating electrical impulses into mechanicalI-vibrations,-

modulates a light beam in accordance with the electrical impulses to be recorded: The mirror oscillograph recording Optical system's""known heretofore, however, have thedisadvanta' ethat the light flux from thereco'rding light source, such as the vfilament of an incandescent lamp,

'isnot efliciently utilized'thereinl This unfavorablecondition is due to the fact that the aperture of .the 'oscillograph mirror the limiting aperture in the two co-ordinate" planes of the known optical systems, and that it cannot be enlarged beyond a certain degree since. the physical size of the mirror must be comparatively small in order to-avoid distortions due ftp its mass. For a given light source, therefore, the amount of light flux reaching the movingfilm is unduly limited'in those optical systems, and this'limitation makes itself particularly felt' when filters are used at some position in the optical system, for'example; for selecting light rays of a or for other purposes.

Another drawback or the knownmir'rcr oscinQ-f r graph recording optical systems is that apo'rtion oiithe, light flux fromthe' recording light source is not effectively preventedthereinii'rom. falling on parts other than the osclllograph mirror, or on the structure housing theoptic'al system. This portion of the light flux' is to some ex-.

tent reflected dififusely,'thus forming stray light certain wave length;

8 Claims. (01 885-24) mademuchlarger than cillogriaph mirror,

he aperture" or the os- Another object of the invention is the provision of such an opticahsystem wherein .the Iormationoi stray light is reduced-tea: negligible amount. l

j Another object'loi' the invention :is the projvisionjdf, such an optical ystem which is particularly satisfactory v as regards ease ;of manufacture'an'd convenience of adjustment..

1 Another object oftheinventionis the provision oi such an'optical system which-may be built' with 5 small 1 physical size and at: comparativelyilittle cost. a

,Still e her Ab eaQOi-memventmn include those vwhich arehereinafter stated or apparent; or which are incidentaleto; the." invention.

In the optical systemv according tdthe invention, the oscillog'rapnmirroris adapted tovibrate about a horizontal axis whilethe-film moves ast f the recording. point fln a substantially vertical direction, therecording nointlbeing' the point at which the optical axis-oi,- the system strikes the films; The optical {system also has means for forming a light spot oi verticall graded light flux, Further meansare provided-in the optical system which effect an'imagery of this light spot in s'uch'amanner that.:it-isconiugate to the recording point ln'hothj'the vertical and horizontal planes of the optlgia glfsystem'. "Otherwise, however, the imagery of the light spot is diiierent in the two co-ordlnate" planes. Inthe vertical plane,

.theilightspotjlsfijlgst iinaged at a horizontal slit by imaging means'fictifigin the vertical-plane and thenat the recordirigipointjby imaging means acting in only the vertical plane, the horizontal slit being placed ghetween-the oscillograph mireven'though thesurtaces onwhich it is incident I may be black. Such stray light is objectionable because it may'cause an additional exposure of the moving film, which should beexposed .only

to light flux modulated by the oscillograph mirror.

It 'is, therefore, the primary object 'oflthe present inventionto provide a mirror .oscillo'graph recording optical system which is highly efllcient as regards the utilization of the light flux from therecor'ing light source. v I Another object of the invention is the provision mi-and therecoi'tlir'i'gijpoint. 'In the horizontal plane,- on the other vhand, an intermediate image of the light spot) is iorrned substantially on the mirror byfirst imaging means which act in only the horizontal planeg'a'nd the intermediate image is imaged at the recording point by second imag: ing means whlchglilgewise act'inonly the horizontal plane. By'v e or thisarrangement, the mirror is substantially at 'a, common focus of two imaging means which act'in' only the plane contaming-its axis'otifvibration, and the limiting aperture injthef'liorizontal plane is the aperture f I of the second imaging means, The aperture of the second imaging means, jhqwever, can be made of such an optical system whose limiting aper-..'

ture can, in one of its co-ordlnate planes; be

as much as five tim I I jif'as largeas the aperture of the oscillograph mirror; l

The means for forming the light spot, finally,

include a recording lighiisourceand ascreen with an opening. The openijngis -illiiminated'aby"light flux from the lightsource; and its intermediate image is formed substantially on the ,os'cillograplr mirror as has been explained hereinabove'. At

amount; I i H In the foregoing briefv explanation of the state of the art an'd summary, of the invention, and

throughout the presentspecification; the: term- "co-ordinate planes" designates. two planes' at right angles to each other whose'line} of inter-, section is the optical axis of the .The'- horizontal plane is .the'cog-ordjinate Pi -3e which contains the axisoi' the oscillo'graph mirroreiid' the slit, whilethe've'itica'l' planeis th'e'co iil'diiiate planeat right angle's tothe liorizontal:'plan& The plane ofthe slit, finally, isthe plane-which con"- vertical and horizonta1 planes;

In thepresent specification; the'termwvertical.

and horizontal thus .are not use inany 'absoe tains the slit, mi is at 'rightangles-,toboth the lute sense butlmerely'sin order to" distinQuish between two" planes, or directions,'. at right" angles defined bylamp' filament Ill and opening it proceeds through the optical system and is deflected vby the mirror H of an 05011103184311 galvanometer (not shown) or similar device for translating electrical impulses into mechanical vibrations. It

thushas a part which is incident" from opening upon: irrori'l, and apa'rtwhich is reflected 1i nr'mi'rroril' towards the recording point 21. vRecording,point 1''! is the point at which the optical axiszot the system strikes the fllm 23, andmove's'past recording point 21 in a substantially vertical direction as indicated by the More pa v 'lciila-rly, opening I3 is an isosceles triangle whose base extends horizontally, and is, adapted to vibrate about an axis l 8=-|E8whi'oh likewise extends horizontally. Fur- 'therrnoreahorizontalslit 2| is formed in a screen l l'zwlfiich' is placed between mirror I! and recordirig'pointfle- A- spherical condenser lens I 2 is placed between l'ai'i'ip' 'i'i and-screen, l ljarid a cylindrical lens 15 which 'hasits cylinder axis vertical, is placed be" "tween screen llv and mirror I]. In front of mirr011: H there is placed 'avsecond spherical lens i9 which acts; on the reflected as well as the incident part of thjejli'ght-b'eam proceeding through theopto one another, andchoice between -those terms-"- scription and illustrationhas been determined solelyby convenience in de- Theinvei tioir will be better. .iinderstoodw th-en the following ti iieii tioiiv is consideredtwithlthe tical system. Asecond cylindrical lens which "also it's cylinder axis vertical, is placed be- "tweenmirror "l1 and screen 22, while a third 'cy- 'lindri'ca'l lens 41 has its-cylinder axis horizontal.

"- -and' isplaced between' screen 22 and recording filioirit 21. I These flve' imaging means have focal lengths ec m y ne.dr l e cert in presentimpreferred embodiments thereof, and; its scope will": be pointed out in; the appendedj claims".

In the drawings;

Fig; i is diagrammatic net neetive: view em optical system embod ing; the invention; 851 8 a ia rammatic l nsit di al s i i n i the vertical plane of the optical systemishown in- 'Fig. 1,: the optical axis being representedwas a straight line and an osclllographmirror as'an' aperture, I Fig. 3 1;, a correspon lfl's sectiorrin the hon-:- zontal'plan'e, Q f I 1 Fig. 4' is an elevation ot-alpart'of theoptical-system of Figs. '1 to'3,

Figs; 5 to we show in elevation meditates of the part shown in Fig; 4,]. e Fig, 11 is afdiagrammatic;perspective" viewof a modification of the optical systemshown in Figs. 1'to3; ".1 i

Fig. 12, is a perspe; ve' of a modification] oiapartshowninFig',1 1,

Figs: 13 and 14 'are'perspectivejviews of modie fications of two other parts oiith'e optical system of Figs. 1 W3;

Fig. 15, is a iiig ri'iiii i i iit e longitudinal section in the vertical plane oi" another, modification-oi;

the optical system of- Figs I to;3,and: I

Fig. 16 is a perspective-view jot amodiilcatlonof still another partol'the DQ131681? system of Figs; 1 t0 3.

Referring first to; Fi g's.f1 to"3; these figures; show, by way of example, a variable} area, recording optical system which ,embodiesthe'finv en -w tion, The, optical system: has; a light sourcesuh as the filament I'll-of; an incandescent lamps. lig.v

The light flux-from lampr filament' t0"uni 1' ormly illuminates a triangular opening i31in' a; screen" I4: so that a, uniformlyillu'rni' 'iated; triangular light spot isformed; atscreen M. 'lhe'lig'lit relative 'to' the other parts of the optical system 'spherieai ensiriies one or its conjugate m1 at lamp filament Ill, and the other substantially at mirror II; that is, either on mirror l1 or at a position close thereto; Cylindrical lens I5 has one of its conjugate feel at opening l3, and the other substantially at mirror I! so that an intermediate image ofop'enin'g" I3 is' formed substantially on mirror' I 1.} Spherical lens l9 has, one of its .conjug ate 1601 at opening l3, and the other at slit 2|. Cylindricalilens "has one of its conjugate foci at the intermediate image of opening I3, and the other-at recordin'g'tpoint 21'.- Cylindrical lens H, finally, has'fone' ofits conjugate tool at slit '2 Land the otheratf-recording pointfl. r Byvirt'uel of the arrangement described here- ,inab'ove-ot its various parts, the following imagery is. performed'in the optical system of Figs. 1't o 3:

In the vertical plane (Fig. 2), spherical lens I! iorms an image I of the uniformly-illuminated opening -i'ii'. inthe plane of the horizontal slitil.

This image of opening l3: moves vertically across :slit; 121-. when mirror i'I vibrates about the horizontalaxis' Hi -l8; As muchof slit Zlas is 11- luminatedby the image of opening I3, is imaged at recording point 21 by cylindrical lens H. Therei thus is'formed 'at recording point 21 a-horizontalwline image or they illuminated portion of slit 2|, and his line image has sharp and distinct horizontal boundaries. Likewise in the vertical plane, spherical lens l2 forms an image of lamp filament;- Hlysubstantially 0n mirror l1, thereby filling mirror with lightand also aidingin the uniform illumination of opening lit by lamp filament'l'fl .v i

N In;theho rizontal Plane (Fig. 3), cylindrical lens I 51 forms substantially on mirror i'l'the intermediate image ofopening I3, and an image of'the intermediate image is formed by cylindrical lens It atgrecording, point 21. By virtueof this suc- *hence acts'in only the verticalplane; I -'I'he=--imagery="'perforiiied in the vertical andton-a "horizontal line :throu'gh opening 'f l I "to'cylin'dric al lens Jl'; is alsoicohi I I I "The line image at recording. pb ir 1't 2-H1ehce .-cessive imageryci opening I; inthe horizontal plane, the horizontal line. image; at recording point ,e .21 has in addition to itssharp and idistinct horiglzontai boundaries, also sharply defined en'dsn i I Lenses 12 and-i9 are spherical and hence have 4 power. in the horizontal as well asin the vertical ,-p1an e. But their actions in .thehorizontal plane can be disregarded for the followingreasonsz? on account" 01 its position and relative focallength, spherical lens 12 'tends-Yto-image lampilla :ment I l I substantially on:- mirrorfslfil, also in i the .drical lens l 5 interferes with this =imagery to' such an gextent. that it becomesimmat'eriai for 'attai'njing the objects of the presen'tiinventi'dm Qntheg I other 'hand,- the power of sphericalhlens I9 iri'the horizontal-plane has noeflectupdn; the actions of cylindrical lenses I} and on account of'the vproximityot spherical'lensii;9-to niirror H which is", in the horizontal plane. substantially at' a' com ,mon focus ofcyl'i-ndrical lenses -l'-5" "ajnd 40. '"No actions, therefore, of sphericalf lenses I2 -a'n d i9 have been indio'atedin Fig.8;

Cylindrical lenses I5 and 1a;- in their-turn"; do

not" interfere with the imagery iiithe vertical plane since theyhave their cylinder axes vertical 'and hence act in only'the horiiontalfplaiie. Correspondingly', cylindrical-' lens;4,idoes not inz-terfere with the imagery-inthe' horizontal plane since it has? its cylinder axisfhoflzontah' ahd horizontal planes of the opticalsystmof Eigs.

' '1 to 3111115 brings it Eboiglt thBt i'ecoi'ding' poiht- 21 isconj'ugate to openihg li in'bothco o' di "planes; In the vertical plane-, horizontal;

is,' with respect to spherical iens 1- 9,- flcoiiiugate ample; the lbrokenjl'iineya-w shown is an image of line a--a as ,faria its vertical extension, or 'width', is eancem aam t is: ac-

cording to a well known propertyoi conjugates, made up of the light flux emanating iromiline a ing point 21 isgconju'gateto li'n'e-bb at thefone 5 A variable area-track 2-8 th'iis'is produced cordahce with the vibration of mirror- IN and, therefore-,.-the electrical impulses to be-recorded.

conjugate to-opening' H orfniore' exthe horizontal? wellfas' the vertical plane ofsthiopticalsystem of Figs; 1 to 3. The Fun-- zagerm howeyer, I I I I I a mament-im m two'--'oil-ordinate plari'es. In

1 which results j in this "condition,

tile-"Vertical plane-, opening) is imag eaesnt :Zifibi sphericallensj F8 whiclii ald'ts'in the vertical plane, and slit '21 is imaged at recording 'fpoint i iil stantially on mirror i'i-by cylindrica I "this; intermediate- 'image is imaged' at re''cording -poiritv2 l by cylindrical -1ens*40i= Since cylindrical lenses i-5' :ahd lfl f'aht' in only 'the' h'orizohtal :plan'e; im'irror I11" issubstantially --a't---a conirnon 'fOCllSz-bf two imag'ing-mea'ns which' act in only githeplane' containingits axis or vibration i8. jon any given angle or flinclinationoi mirror 11, ;t-herefore,:=:the amount: of light -flux:-'-froni opening l 3 *Wh'ich is acted upon; cylindrical i'en's his-limitedabythe 'zaperture 61 this 1ehs "ratlier than the aperture of mimosa-Irma aperture *0! :;cylindri'cal-s lens 40, however g" be' made as focus at recording p oint i ZTal'soin the horizontal plane, namelyf as i has j been explainei'i herein}- above--'by the successive imaging aotioxi's,ofjfcy lindrical lehs'es- IB and Ill. The line imagejatf re.-

- cording point 2! hence is anfimage o'flinea-a also as far as' tg horizontalextens'ioh; 'iorjffie ath,

is concerned. Whenfi therefore, I the. horizontal line t u h 9mm? lljjissh ift fls, i i ior "exism ie; the broken line Fig.f "4- -the ine image is'also short whileiti'is; long'when that hb i; zontal line is long-=as 'iS'J'fQrI example, the broken nometer on which it is mounted, m q'ramg' oms 21 is iconjugate to=line*d =a-, ameniiiie pas es ice through opening I! hallway betweeni its tipani its-obese. When thezrthe electrical impulses to be recorded are applied in-iknown -manner 'to the oscillograph galvanometergnmirror l1 vibrates in. accordance therewith about the horizontalam's il-f-la and in such a mannerthat; whenthe amplitude of its vihr attion is a maximum, record iitisapraoticalto give tom'irror-II;

- through opening l'i-i'which hecomeoonjugatef to recordingtpoint l i-i 1;

'-:--'-In;th'e liorizonta1 piane',-'on tlieoth' ha nti Q an intermediate image of ope'rling f I3 is much as five times as large as the aperture which @The" resultthus obtained- -bynieans=of the no'vei imageryembodiedi' 'by-i way oiexar'nple,-"in the nurror 'oscillograph' recording optical -'sy' stem "of Figs. '1 to=3=represeritsjaniarkedadvance over vthe-prior art: In the opticalsystenis; the light; flux-'from-the entrance ho'sition correspond- =ing: t oz opening i3 is diffused at the 'oscillog'ifaph mirror; inithe two co-ordinate planes o that the mirror aperture as 1 the limiting aperture of th'e optical: asystems also l'l'l' the Gil-0111ii'iate Diane which contains the n-iiri'oijaxisif -since-the physi ca lj size 0L the-iosoillographmirror' must be com parativel yl smallin order t'o' avoid distortions o to dts ma'ss; 'the'a'bove'conditiori has been a serious *obstacle" to, an" ancient-utilization of the light mix in t1ie prior art opticals'y'steihsJ Theaiiyantage gained in this respect by the imagery aecorgiing to theimiention isconsiderable because, as is well known-to those-skilled 'ifr the" art} the efliciucy with-which the light flux from -agiyenIiightsource is utilized in-'. an} jitical'systen is "apfiroii at'ely proportionalr-to'th -product of*tlieliniitihg pe turesin'thetwo-coeorrlihateplan f of the-optical sys e c Another-a vantage} r navmg',fl n tiie pea -e1 system- 01? Figs. 1- to 3;-mirror -l1 s i ihstantiall'y'at a conimon focus of two gim'agi'ng meanswmcnactj m onlyithe nori ontarpmne,'isthatsmaiideviations of mirror "about a vertical axis have a negligible eiiect onthe imagery in the horizontal .plane. Mirror I! need therefore be accurately adjusted only about the horizontal axis i8--l8. This greatly increases the ease of adjustment ofthe optical system, and is particularly important lengtha't only one of its ends, are formed at vi recording point 2'! so that two unilateral variable when it is necessary to replace the oscillograph galvanometer on which mirror I l is mouhtedz.

. ,Afurther advantage. of the imagery performed in the cpticals'ystem of Figs. 1 to 3 resides inithe fact thatthereis formed substantially .cn mirror l1 an image of iampjfllament Ill by the action; of

sphericallens II'Einthe--vcrtica1 plane,'and simul taneously the intermediate image of opening l3. by the'action of cylindrical lens 13 in the horia; zontal plane. It thus is'possible' so to-co'ntrol' the light flux entering theioptic'al system through;

opening l3 that it is all incident within the a working aperture of mirror IT. This result is best j obtained when the focal length of spherical-lens I2 and the position of lamp II are chosen so that the image ctlampiliament I has a vertical dimension no larger than that or mirror, l1, and when the focal length ofcyllndrical lens l and the position of screen H are chosen so that the largest horizontal dimension of the intermediate image is no larger thanthe horizontal dimension -ple, by'providing in screen It two right-angled triangles adjacent to each other along a common area tracks are produced on film 23. With opening 32, finally, there are formed at recording point -21 three horizontal lines of light, each varying in. length at bothits ends, so that three sym- I .metrical variable area tracks produced on film 23.

are simultaneously Tracks'of th'e'type known as push-pulY'may alsolbe produced on film 23 by combining in 'SCIBfil'ltl .two openings of the kind described hereinabove. For example, the two openings may be two isosceles triangles 33a and 33b arranged I as shown in Fig. 8. or two.right-angled'triangles 34a and-34b arranged as shown in Fig. 9. With openings 33a and 33b, a class B push-pull symmetrical variable area track is produced, and with openings 34aand 34b 2. classB push-pull unilateral variable'area track. .Class A-push-pull variable area tracks may be produced, for examside b-b so that together they form a parallelogram 35, as shown in Fig. 10. In a preferred arrangement for the, production of class A pushpull variable area tracks, however, a portion Ila of screen It separates the two right-angled trianotmirror i]. If these conditions are fulfilled,.al1

. thelightfiux passing through opening I3 is subject to control by mirror ll, whereby the formation of stray light in the Optical system is reduced t-oanegligib1eamount. e 1 The employment, finally, of cylindrical lens H in the portion of theoptical system between screen 22 and recording point 21 has certain in-- herent advantagesz. Cylindrical lens 4| may have ashort focal length soxthat the optical system may be builtwlth small physical'size. Moreover,

a cylindrical lens'oi short 'focal length'is. less .expensive than a spherical lens, or lens system,

well enough corrected .to form, over the same distanc, an equally sharp line images The optical system of Figs. 1 to 3 mayhence be built with greater compactness and at less cost than the mirror oscillograph recording optical systems known heretofore.

The optical system shown in Figs. 1 to 3'as' an embodiment ofthe imagery according to the invention may be modified, without aflecting the gles 35a and 35b, as shown in Fig. 10a.

. As in Fig. 4, the broken line a-a indicates also in Figs. 5 to 10a the horizontal line through the opening, or openings, in screen M which is nor- .mally conjugate to recording point 21 when mirror I! is at rest. The openings of vertically varying horizontal extensionv shown in Figs. 4 to 10a, and described I hereinabove, all are bounded by one or more straight edges which. are inclined with respect to the horizontal plane of the optical system. Since,

furthermore, the variation in length of the horizontal line, or lines, of light at recording point C2] is effected only .by those inclined edges, the .lower portion of screen H may be omitted if 'desired, as indicated e:-e, forexample. I 'When any of the openings, or pairs of openin Fig. 5 by the broken line ings, shown in Figs. 4 to. 10a is in screen It and receives light flux from lamp filament [0 through spherical lens l2, there-isiormed at screen ll a uniformly illuminated light spot whose horizontal extension varies in a. vertical direction, or a pair of such light spots. The light. flux emahating frornthis light spot, or light spots, hence is vertically graded.

anglewitn one of 'the sides adjacent to the right angle extending horizontally as is the opening 30. shown in Fig. 5, or; there :may one? or more sawtooth projections extending into it as they do into openings 3land 32 shown in Figs. 6 and "7, respectively.

However, in the case of opening l3 the line image at recording point 21 is, a horizontal line of light whoselength varies at both its ends so i that the variable area track produced on film 23 is symmetrical as is the track 28 shown in'Fig. 1. With opening 30 on the other hand, the line image is a horizontal line of light whose length varies at only one of its ends so that the variable area track produced on film 23 is of the unilateral type in this case. With opening. 3|, furthermore, two horizontal lines of light, each varying in Light spots of vertically graded light flux, however, may also have auniform horizontal extension and a vertically varying illumination. Means for forming a lightspot of this type are well ,known in the art. Theymay consist, for example, of the means disclosed by.G. L. Dimmick in his'UpS. specifications 2,095,317 and 2,095,318.

'I'hesemeans include an opening 36 which is a rectangle with one of its sides extending verti- U. S..specification 1,955,386 of this specification;

cal1y,and a penumbra stop 31, as shown in Fig. 11. But the illumination oflrectangular opening 36 may also be varied vertically by associating with opening 36 a vertically graded light shading member 38 such as is disclosed, for example, in my and shown in Fig. 12

- Whe these or other suitable means for forming a lightspot of uniform horizontal extension and vertically varying illumination are substituted for opening I 3 in the optical system of Figs. 1 to 3-- as shown byway of example in Fig. 11- the line image at recording point 2! is a horiin the horizontal plane. 1

zontal' line of light whose length is constant, but

' by considerably lengthening theoptical system whose illumination varies inaccordance with the vibration of mirror H. Hence, a variable density track 39 is-now produced on film- 23 as it moves past recording point 21.1

(2) Condenser lens I2 is shown in Figs..l.to 3

and 11, and has been described hereinabovaas being spherical. It hence acts in both the vertical and horizontal planes. However, as has been pointed out hereinabove, its action inthe hori-- zontal. plane is immaterial as far as the novel imagery disclosed in this specification is conmechanically." However, this end may be accomplished in a more convenient way which, at the same time, provides for a very. compact mechanical design of the optical system and which is shown, by way of example, in Fig. 15. It consists of placinga reflecting prism 10 between screen It and mirror I! whereby the light beam is folded so'that it is incident upon mirror" at a small angle, and cylindrical lens H is traversed by both the incident'and reflected parts-of the light beam. In'place of prism 10 there may be cerned. Spherical condenser lens l2 may therefore be replaced by a cylindrical condenser lens 65- which has its cylinder: axis horizontal and hence acts in only the vertical plane. I Like spherical lens I 2, cylindrlcallenslii has one of its conjugate tool at lamp filament. I 0, and the other substantially at mirror I]. Cylindrical lens 65 may, furthermore, hav the same position as sphericallens l2, in which position it is shown in Fig. 13. But 'sin'ceit actsin only ithefvertical plane, it mayalso have any other position between lamp II and mirror 11' wlr' ich'isconsistent with its function to image lampffila'ment l0 substantially on mirror j ly 1 employed other suitable beam folding mean such as mirrors, or the like.

(5) Whenever it is desired to employ for the imagery in the horizontal plane of the optical system two lenses instead of the single cylindrie cal lens ll, cylindrical-lens 40 may be replaced by a spherical lens 15 which, however, must be placed adjacent to screen 22 as shown in Fig. 16.. When spherical lens 15 is so placed, its action I in the-vertical plane is barred'by screen 22 so that it acts in only the horizontal plane. Spherical lens 15 may be placed on either side of screen In designinganTactual-opticalsystem withLcylindrical condenser lens .65.- however, the horimade' so great thatthebpening in screen I, as seen from cylindrical lens 1551s completelyfilled 'Withlight. o f. P

(3) It' has been explained hereinabove that, while spherical lens -19] "power in both the vertical andf horizontal planesfitsjaction in the horizontal plane can be. disregarde'd. Spherical lens I9. may therefore :be replaced} by, a cylindrical lens 66 which'has its cylinder axis horizontal and hence acts "in only the vertic'al plane. Like spherical lens i9, cylindrical lens. has one. of

its. conjugate fool at the opening iinscreen I4, and the other at slit ,2.l-. Cylindricallens may, furthermore, have "the same position as spherical "lens ,I 9, inwhich position yit: is shown in Fig. 14.

But since, it acts :in only-the vertical plane, it may also have any other position between-screens II and 22 which is consistent'with its function to image the =opening-in'screen II in the plane of slit 2|. Spherical lens" [9, on the other hand,

should be placed close tomirror as'shoWn in Figs. 1' and-.11,; lest'it interfere with the imagery (4) When the light beam defined by lamp filament In andthe openingin' screen It is incident 7 upon mirror". at a suillciently small angle, a single cylindrical lens- Il .may besubstituted for the two cylindrical lenses ligand 40. j Likecylin drical lenses l5 and Ill, cylindrical-lens 'II has zontal,extensionjloflampyiilament ill should be o 22, but must be closethereto in both cases lest it interfere with the imagery in the vertical plane. Like cylindrical lens 40, spherical lens 15 has one of its conjugate tool at the intermediate imageof the opening in screen [4, and the other at recording point 2|. The substitution of spherical lens 15 for cylindrical lens 40 has the advantage that a spherical lens at screen 22-is cheaper,

' and easier to adjust, than acylindrical lens. The

3 portions of'which this track. consists, be sharp and welldeiined'. The horizontal line, or lines, or

, light formed atrecording point 21 must, there'- ior'e,fbe sharplydeflnedat its, or their, ends. For

that reason, cylindrical lenses l5 and 40 should preferably be well corrected for spherical and chromatic aberration, and for coma. This applies also to their substitutes, namely, cylindrical lens H and spherical lens I5. However, if any or all of the above lenses are not so well corrected, the beneficial results accruing from their employment in accordance with the present invenits cylinder'axis vertical, and it is placed so as to be traversed by the reflected as well-as the incident part of the. light beam proceeding through the optical system. The relative focal-f length of cylindrical lens 1| .is'sochosentthatthe opening in screen. and-a'position on, or

close to, mirror I! are conjugate with respect to cylindrical lens Iiv on the incident part,-andthis position and recording point 21 are conjugate with respect to cylindricallens II on the reflected part of the light beam. In this manner,-.cylin-.

drical lens ll forms the intermediate image or theopening in screen It substantially onmirror ll and, simultaneously, images the intermediate image at recording point 21. I

Th angle at which the light beam inicident v imaging means placed in front of said mirror, and

uponmirror I1, may be made sufiiclently small tion may still be had, although to a lesser extent than if they are well corrected.

(7) Ii it is desired to em loy the optical system of Figs. 1 to. 3 for recording sound in accordance with the method generally known as noiseless recording," the well known ground noise reduction systems may be used in conjunction therewith, aswill easily beunderstood by those skilled in the art.

What is claimed is:

1. In an optical system, the combination of means for forming a light spot of vertically graded light flux; a mirror adapted to vibrate about a,' horizontal axis; means .forminga horizontal ,slit; a-recording. point pastwhich afilm may move in a substantially 'verticalfdirection; first imaging means placed between said light spot and said mirror, and having first and second conjugate loci; second. imaging means placed between said mirror and said slit forming means, and having third and fourth conjugate foci; third 11 having fifth and sixth conjugate fool; and fourth imaging means placed between said slit forming means and said recording point, and having seventh and eighth conjugate foci: said first ima ing means acting in only the horizontal plane and having saidfir'stfocus at said light spot, and said second focus substantially at said mirror so that an intermediate image of said light spot is formed substantially on said mirror; said second imaging means acting in only the horizontal plane and having said third focus at said inter-- mediate image, and said fourth focus at said recording point; said third imaging means acting in the vertical plane and having said fifth focus at said light spot, and said sixth focus at said slit; and said fourth imaging means acting in only the vertical plane and having said seventh focus at said slit, and said eighth focus at said recording point.

. 2. The combination defined in claim l'wherein said first imaging means is, a cylindrical lens having its cylinder axis vertical. 1

3. The combination defined in claim 1 wherein said first and secondima'ging means are each a cylindrical lens having its cylinder axis vertical.

4. The combination defined in claim 1 wherein said second imaging means is a spherical lens placed adjacent to said slit forming means.

5: The combination defined in claim 1 wherein said third imaging means is a spherical lens, and

said fourth imaging means is .a cylindrical lens having its cylinder axis-horizontal.

6. The combinationzdefined in claim 1 wherein a said third and fourth imaging means are each. a

cylindrical lens having its cylinder axis horizontal.

7. The combination defined in claim 1 wherein. said first and second imaging means are each a cylindrical lens having its cylinder axis vertical,

said third imaging means is a spherical lens, and 40.

said fourth imaging means is a cylindrical lens having its cylinder axis horizontal.

8. In an optical system, the combinationof a light source; a screen with an opening whos horizontal extension varies in a vertical direction, said opening being uniformly illuminated by said light source; a mirror. adapted to vibrate about a a horizontal axis; means forming ahorizontal slit;

foci; a. second spherical; lens placed in front of said mirror',..and having-seventh-and eighth conjugate foci; and. a' third cylindrical lensplacedv between said .slitformingmeans and said recording point, and, having ninth. and tenth conjugate fociz saidfirst spherical lens. having said first focus at said; light source, andpsaidsecond focus substantially at saidv mirror; said. first cylindrical lens having. its. cylinderaxis vertical and 'hav-;

ing said thirdufocus rat said opening, andsaid fourth focus. substantially at said mirrorfso that an intermediate image of'saidi opening is formed substantially on said mirror: said second cylindrieallens having its cylinder axis vertical and having said fifthfocusjat 'saidiintennediat image, and'said sixth focusatlsaid recording. point; said second spherical lens having said. seventh focus at saidfopening, and. said eighthfocus at saidslit; and said third cylindrical. lens having its cylinder axis horizontaland, havingsaid ninth focus at said slit, and said tenth focus at said recording point.

, JOHNA. Ja.

REFERENCES crrnn,

The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,157,166 Dimmick May 9, 1939 2,173,681 .Dimmick- Sept. 19, 1939' 2,125,890 Cook Aug. '9, 1938 2,256,402 McLeod et 'al'., Sept. 16, 1941' 1,999,721 Dimmick Apr, 30, 1935 2,121,568 Newcomer June 21, 1938' 1,847,636 Taylor Mar. 1, 1932 2,052,220

Dimmick Aug-25, 1936 

